Evaluation of New Winegrape Varieties for the San Joaquin Valley

Twenty winegrape varieties were planted for viticultural evaluation at the Kearney Research and Extension Center (Table 1). Degree days, calculated from March 15 thru October 15 using a threshold of 50??F, regularly reach 4500 placing it in region V on the Winkler scale. Many the varieties are being evaluated in California for the first time. We believe that newly imported winegrape varieties from around the world may have beneficial characteristics that will make valuable contributions to the California wine industry. Identifying these varieties is the goal of this continuing research. The first usable data was collected from this trial in 2007. Therefore the 2010 season provides the opportunity to present both the current year?s data and average data from four years. All varieties were pruned and shoot thinned to 15 shoots per meter. The protocol called for all varieties to be harvested at 24 Brix. In 2010 harvest occurred from September 9 to October 20, a 41 day period. Mean harvest Brix across all varieties was 24.1. Eleven varieties were harvested within 0.5 Brix of the 24 Brix goal. Tempranillo was harvested on the last day at only 20 Brix and was no longer accumulating sugar. Yield ranged from 2.7 ton/acre (Carmenere) to 12.3 (Grenache). Interest in this project resulted in a collaboration with Constellation Brands, Madera. For the third year Constellation agreed to make wine from selected varieties. The results will help us more thoroughly describe these varieties. A detailed review of each of the 20 varieties is included in the interim report. Recommended varieties include Durif (Petite Sirah), Petit Verdot and Tannat. The cooperation of Constellation Brands, Madera in Brix sampling and in winemaking and analysis is greatly appreciated.